Optimising Drilling in Composites

Composite materials are favourited in manufacturing due to their high strength-to-weight ratio, specifically, for performance-critical applications, where reducing weight directly enhances efficiency, speed, and fuel consumption [1]. Additionally, their corrosion resistance and design flexibility, allow manufacturers to create highly specialised components that are used across multiple industries such as aerospace and automotive [2]. 

However, manufacturing composites presents different challenges compared to traditional metals – drilling, especially, unlike milling or turning, is particularly complex due to their heterogeneous nature and the continuous tool engagement throughout the cutting [3]. Exactaform’s engineering approach to drilling in composites focuses on tool innovation, process optimisation, and machining strategies that allow manufacturers to drill composites more efficiently, with higher precision and extended tool life. 

Understanding the Challenges of Drilling in Composite Materials 

Traditional metals, like aluminium, steel, and titanium are homogeneous, meaning they have consistent mechanical properties throughout. In contrast, composites consist of multiple bonded layers, often with reinforcing fibres embedded in a polymer matrix. Even though, these fibres provide structural strength, the downside is that they are highly abrasive, while the matrix is prone to heat-related damage. [4] [5]  

Furthermore, composites are anisotropic, meaning their strength and mechanical behaviour vary depending on fibre orientation, resin distribution, and layering. This makes them behave differently under machining forces which makes their manufacturing even more challenging. [5]  

• Delamination & Splintering – Composites are unable to absorb cutting forces uniformly, which can cause layers to separate. This could weaken their structure and could also require additional finishing operations.  
• Tool Wear & Heat Generation – The abrasiveness of carbon and glass fibres can cause tool degradation, while the polymer matrix does not dissipate heat efficiently, which could lead to excessive tool wear.  
• Resin Smearing – At high temperatures, resins can soften and adhere to the tool, affecting cutting accuracy and increasing friction. [6]  
• Burr Formation & Fibre Pullout – Incorrect cutting parameters or improper tool geometry can pull fibres out of the composite structure, leaving rough edges that impact fit, bonding, and load distribution in the final assembly. [6]

The Exactaform Approach to Composite Drilling 

Drilling in composites requires a high understanding of tool mechanics, material properties, and process control. Rather than just following a general approach, Exactaform’s process can be broken down into three main points. 

1. Selecting the Right Drill for Composite Materials

A traditional drill often struggles with composites due to its inefficient dust evacuation. As composites produce fine dust-like debris, they require specific cutting geometries and high-performance cutting tool materials to maintain manufacturing efficiency and tool longevity. 

• PCD Drills have the longest tool life, offer minimised delamination, produce highly precise cuts, and often guarantee the best cost-per-part. 
• Carbide Drills with Diamond Coating is a cost-effective alternative to PCD, better for low batch work where cost-per-part is less important. 
• Solid Carbide Drills are better suited to short production runs, though they wear faster due to fibre abrasiveness.

• Brad Point & Multi-Faceted Drills create a clean cuts and minimise fibre breakage. 
• Compression Drills (Split Point Geometry), which feature opposing cutting edges, counteract delamination forces. 
• Double Margin Drills are designed for roundness and surface finish and reduce the need for post-processing.

For hybrid stacks (e.g., CFRP-Titanium or CFRP-Aluminium), carbide drills with coolant-through capability improve tool life and thermal control.

2. Optimising Cutting Parameters for Composite Drilling

Fibre brittleness and heat dissipation can be minimised by optimising cutting speeds and monitoring cutting forces. Exactaform’s engineers create tools that are adjusted to fibre orientation and resin composition; we perform predictable tool testing in house and can advise on cutting force monitoring and heat build-up evaluation post-production. General things to consider:  

• Peck Drilling Cycles – Interrupting the cut allows heat dissipation and prevents dust build-up. 
• Controlled Exit Feed Rate – Slowing down at breakthrough minimises splintering and exit burrs. 

3. Enhancing Process Control for Composite Drilling

Beyond tool and parameter selection, maintaining process stability ensures consistency and long-term efficiency. Effective dust evacuation and dust control play a crucial role in this, with dry drilling and minimum quantity lubrication (MQL) as the two primary approaches. 

• Dry Drilling is commonly used in aerospace applications to prevent contamination. 
• MQL enhances tool performance by reducing frictional heat and assisting dust evacuation. 
• Effective Dust Extraction Systems are critical to preventing tool damage and maintain a safe work environment in CFRP machining. 

Advanced Machining Techniques 

• Orbital Drilling – Uses a circular tool motion, minimising heat and improving surface finish. 
• Cryogenic & Vibration-Assisted Drilling – New techniques that reduce temperatures and extend tool life. 

Why Choose Exactaform? 

Our 45 years of expertise in PCD and carbide tooling is backed by application-driven innovation. We help manufacturers find the best tooling solution through developing the right combination of drills, cutting parameters, and process control techniques to ensure cleaner cuts, longer tool life, and higher machining efficiency.  

• Longer tool life with PCD and diamond-coated carbide drills 
• Optimised cutting strategies tailored to composite materials 
• Advanced process stability for reduced defects and improved efficiency